Artificial turf with granule retaining fibers

ABSTRACT

An artificial turf is provided that resists migration of rubber infill into the space above the turf. Artificial grass is attached to and extends upward from a backing material, which may be one or more layers. The artificial grass includes groups of at least two different kinds of fiber sewn through a common path in the backing material. One of the kinds of fibers is an artificial grass blade shaped so as to appear like a blade of grass. The other kind of fiber in each group is pre-stressed/crimped so that the relaxed shape of the fiber is nonlinear, resembling a curlicued or articulated form having lateral excursions. The lateral excursions cause portions of one such pre-stressed fiber to overlap and interfere with another, forming a mesh. The height of the pre-stressed fibers in their relaxed state in the turf is less than the height of the relatively unstressed fiber(s). Resilient granules are embedded in the mesh, and are captivated by the interfering pre-stressed fibers. In one embodiment, the pre-stressed fiber is constructed of nylon material, and the relatively unstressed artificial grass blade of polyethylene.

FIELD OF THE INVENTION

The present invention relates generally to artificial turf, and moreparticularly to an artificial turf including a plurality of groups, offibers, each group including both straight and non-linear fibers sewninto a backing through a common opening, with the non-linear fibersproviding captivation of granular infill.

DESCRIPTION OF THE PRIOR ART

Artificial turf is used in a variety of areas, such as on athleteplaying fields for football, soccer, baseball, tennis, etc. Theartificial turf is usually made to simulate a natural grass field. U.S.Pat. No. 5,601,886 by Ishikawa et al. describes an artificial turfconsisting of alternate rows of longer and shorter artificial grassfilaments sewn into a backing. A layer of sand is deposited into theartificial turf so as to cover the shorter filaments. A disadvantage ofthis structure is that the sand infill tends to compact and harden, andhas an abrasive quality.

U.S. Pat. No. 4,396,653 by Tomarin discloses sewing pile fibers into abacking, and then depositing a bottom layer of rubber-like particles,and then a binder for gluing some of the particles together. A secondlayer of sand is then deposited over the first layer wherein the depthof the first and second layers is less than the height of the pilefiber.

U.S. Pat. No. 6,527,889 by Paschal et al describes a structure thatappears similar in purpose to that of Tomarin's, wherein the rubberparticles of a first bottom layer are coated with a bonding agent.Application of water to the layer then activates the bonding agent foradhering the particles together. A second, top layer of rubber particlesis then deposited over the bottom layer.

U.S. Pat. No. 6,299,959 by Squires et al. discloses a grass-like surfaceformed with polyethylene co-polymer slit fibers tufted through afiberglass reinforced backing. Three layers of infill are thendeposited. The bottom layer is rubber granules, and the top two layersare each a mixture of rubber and sand.

The above described patents using rubber granules or rubber and sandmixtures provide a more resilient, shock absorbent surface. Adisadvantage is that some of the rubber particles become air-borne uponimpact with the turf. For example, football players impact turf withshoulders and helmets, etc., bringing the player's faces close or incontact with the turf. The small “rubber granules” are often created bygrinding up used automobile tires, and include the various components,including natural and synthetic rubber and ground up steel belt. Thesefinely ground particles can be ingested by players, and may be a healthhazard, or at least a potential irritant.

SUMMARY

It is an advantage of this invention in that it provides an artificialturf having an improved stability.

It is a further advantage of this invention in that it provides acombination of good shock absorption with stability of rubber infill.

It is a still further advantage of this invention in that it providesimproved retainment of rubber infill in combination with good shockabsorption, and reduces the quantity of infill that escapes into the airabove the turf.

In one embodiment of this invention, an artificial turf is provided thatresists migration of rubber infill into the space above the turf.Artificial grass is attached to and extends upward from a backingmaterial, which may be one or more layers. The artificial grass includesgroups of at least two different kinds of fiber sewn through a commonpath in the backing material. One of the kinds of fibers is anartificial grass blade shaped so as to appear like a blade of grass. Theother kind of fiber in each group is pre-stressed/crimped so that therelaxed shape of the fiber is nonlinear, resembling a curlicued orarticulated form having lateral excursions. The lateral excursions causeportions of one such pre-stressed fiber to overlap and interfere withanother, forming a mesh. The height of the pre-stressed fibers in theirrelaxed state in the turf is less than the height of the relativelyunstressed fiber(s). Resilient granules are embedded in the mesh, andare captivated by the interfering pre-stressed fibers. In oneembodiment, the pre-stressed fiber is constructed of nylon material, andthe relatively unstressed artificial grass blade of polyethylene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an artificial turf according to the presentinvention;

FIG. 2 illustrates two fibers through one needle, and fiber tension;

FIG. 3 is a table of example dimensions of fiber and infill height;

FIG. 4A shows one type of artificial grass fiber construction; and

FIG. 4B shows the fiber of FIG. 4A rolled up.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention will be described herein with reference toparticular embodiments thereof, a latitude of modifications, variouschanges and substitutions are intended, and it will be appreciated thatin some instances some features of the invention will be employedwithout a corresponding use of other features without departing from thespirit and scope of the invention as described with respect to thepreferred embodiments set forth herein.

Referring now to FIG. 1 of the drawing, the artificial turf 10 of thepresent invention is illustrated. A backing material 12 has twodifferent kinds of fiber 14 and 16 sewn into it, with both fiber 14 and16 passing through the same passages 18 in the backing 12. Fiber 14 isan artificial grass blade that can be constructed in a number of ways togive the turf a grass like appearance. Fiber 16 is pre-stressed into anon-linear shape, creating a mesh for retaining infill 24. The tops 20and 22 of the fibers are cut, forming a “cut fiber” carpet/artificialturf, resulting in the fiber 14 appearing grass-like. The fibers 14 arerelatively un-stressed and have only minor deviations from linearity,similar to a linear/straight grass blade appearance. Fibers 16 arepre-stressed prior to being sewn into the backing. During the sewingprocess, fibers 14 and 16 are both threaded together through the samesewing machine needle passages, and therefore pass through the sameopenings 18 in the backing through which the needle is inserted.Axial/longitudinal tension on the fibers 14 and 16 provided by thesewing machine keep both fibers 14 and 16 under tension, and mostimportantly, fibers 16 are held in an uncrimped, straight line. Uponbeing sewn into the backing 12, the tension on fiber 16 is released andit returns to its pre-stressed/crimped condition, that could bedescribed as curlicued. The lateral/horizontal excursions such asexcursion “x” of the fibers 16 provide resistance to migration ofparticles 24 placed in the artificial turf, which most commonly areground up used tires, the resulting granules having a resilient, shockabsorbing characteristic.

In one embodiment, the fibers 14 are constructed of polyethylene andfibers 16 of nylon. The polyethylene has a slick surface which helpsavoid injury from, for example a football player twisting an ankle dueto turf resistance/friction. The dimensions of the stitch spacing S androw spacing R, are selected along with the design of the pre-stressedshape of the fiber 16, so that lateral excursions of a fiber 16 from onepassage 18 overlap the excursions of a fiber 16 from an adjacent passage18. In this way, an effective mesh of fiber 16 is formed that resistsmigration of the rubber particles 24, both upward and horizontally.

FIG. 2 is provided to illustrate the tension applied to the fibers 14and 16 during the process of sewing. The initial ends 26 of the fibers14 and 16 are secured during the process. The needle 28 is insertedthrough the backing 12, taking both fibers 14 and 16 through a commonpassage 18. A hook 30 grabs the loop of fibers and keeps the fibers fromretracting back through the passage 18 as the needle 28 is retracted.The sewing machinery then inserts the needle 30 through the backingagain at a stitch space “S” (FIG. 1) from the first space 18 and thehook 30 grabs the material again. A cutting tool (not shown) followsalong or is integrated with the hook apparatus 30 and cuts the loop ends32, at which time the tension on the cut fiber 16 is released and thefiber 16 returns to its curlicued/non-linear state as shown in FIG. 1.

In one embodiment, the fibers 14 are constructed of polyethylene, andextend upward from the backing a distance H1 of approximately 3 inches.The retracted, rest state curlicued fibers 16 extend upward from thebacking a distance H2 of approximately 2½ inches. The height H3 of therubber infill granules 24 in this particular embodiment is approximately1¾ inches. This combination of heights and other examples are listed inFIG. 3. Other dimensions are also included in the spirit of the presentinvention, as will be apparent to those skilled in the art. In general,the height H2 of the curlicued fiber 16 must be shorter than the heightof the relatively straight fiber 14, and the height of the infill H3 isless than the height H2 in order to optimize the captivation of thegranules, but can also be somewhat higher, particularly if a differentgranule material is used above the fibers 16 that is less irritating tothose who play on the turf.

As described above, the straight fiber 14 may be constructed frompolyethylene, which provides a slippery surface similar to grass. Othermaterials that simulate the grass-like property of lowresistance/friction are also included in the spirit of the presentinvention. The nylon fiber 16 is selected for its resiliency and abilityto hold the ganules 24 in the turf. Other materials for fiber 16 thatwill retain the granules in a similar way are also included in thepresent invention.

The grass-like fibers 14 can be constructed in a variety of ways thatwill be apparent to those skilled in the art for use in the turf of thepresent invention, and the present invention includes the use of theseconstructions in the turf structure as described in reference to thefigures of the present disclosure. FIG. 4A illustrates the constructionof one type of grass-like structure for use as an artificial grassblade. A length of polyethylene or other material of width “W” is slicedthrough in places 38 as indicated. The material is then rolled up, orpre-stressed to automatically roll up, as indicated in FIG. 4B, and whensewn into an artificial turf backing it resembles a blade of grass.

The granules 24 made by grinding up used tires are an example ofresilient material that can be used as an infill. Other materials thatprovide a shock absorbing layer are also included in the presentinvention, including mixtures of resilient and non-resilient granules,such as a mixture of sand and rubber granules, etc.

While the present invention has been described herein with reference toparticular embodiments thereof, a latitude of modifications, variouschanges and substitutions are intended in the foregoing disclosure, andit will be appreciated that in some instances some features of theinvention will be employed without a corresponding use of other featureswithout departing from the spirit and scope of the invention as setforth in the appended claims.

1. An artificial turf comprising: a backing; and a plurality ofresilient first fibers pre-stressed so as to have a non-linear shapewith lateral excursions when not under tension, and a plurality ofsecond fibers shaped to resemble grass blades, wherein at least onefirst and at least one second fiber are sewn through common openings insaid backing, and extend upward from said backing to a cut end.
 2. Aturf as recited in claim 1 wherein said first fibers extend upward fromsaid backing a first height and said second fibers extend upward fromsaid backing a second height greater than said first height.
 3. A turfas recited in claim 2 further comprising particles including resilientgranules positioned in said turf.
 4. A turf as recited in claim 2wherein said second height is in the range of 2 to 3 inches, and saidfirst height is in the range of 1¾ to 2¾ inches.
 5. A turf as recited inclaim 3 wherein a layer of said granules extends upward from saidbacking a height less than said first height.
 6. A turf as recited inclaim 5 wherein said lateral excursions of said first fiber provideresistance to motion of said particles.
 7. A turf as recited in claim 6wherein groups of said first fibers are spaced apart such that lateralexcursions of first fibers of one group overlap lateral excursions offirst fibers of an adjacent group thereby providing a mesh for resistingmovement of said particles.
 8. A turf as recited in claim 7 wherein saidgroups of first fibers are in rows separated by distances in the rangeof ⅜″ to ¾″.
 9. A turf as recited in claim 1 wherein said first fibersare made from nylon.
 10. A turf as recited in claim 1 wherein saidsecond fibers are made from polyethylene.
 11. A method of manufacture ofartificial turf comprising: sewing into a backing a plurality ofresilient first fibers pre-stressed so as to have a non-linear shapewith lateral excursions when not under tension, and a plurality ofsecond fibers shaped to resemble grass blades, wherein at least onefirst and at least one second fiber are sewn through common openings insaid backing, and extend upward from said backing to a cut end.
 12. Amethod as recited in claim 11 wherein said first fibers extend upwardfrom said backing a first height and said second fibers extend upwardfrom said backing a second height greater than said first height.
 13. Amethod as recited in claim 12 further comprising inserting particlesincluding resilient granules in said turf.
 14. A method as recited inclaim 12 wherein said second height is in the range of 2 to 3 inches,and said first height is in the range of 1¾ to 2¾ inches.
 15. A methodas recited in claim 13 wherein a layer of said granules extends upwardfrom said backing a height less than said first height.
 16. A method asrecited in claim 15 wherein said lateral excursions of said first fiberprovide resistance to motion of said particles.
 17. A method as recitedin claim 16 wherein groups of said first fibers are spaced apart suchthat lateral excursions of first fibers of one group overlap lateralexcursions of first fibers of an adjacent group thereby providing a meshfor resisting movement of said particles.
 18. A method as recited inclaim 17 wherein said groups of first fibers are in rows separated bydistances in the range of ⅜″ to ¾″.
 19. A method as recited in claim 11wherein said first fiber is made from nylon.
 20. A method as recited inclaim 11 wherein said second fiber is made from polyethylene.